1. Field of the Invention
The present invention relates to the manufacture of lites (glass sheets or glass panels) which are eventually stacked in relatively intimated, though spaced, relationship to each other.
2. Description of the Relevant Art
It is conventional to stand lites/glass sheets on edge substantially vertically and interleave a sheet of paper, such as craft paper, between the sheets. Such sheets are generally stacked upon a pallet and are enclosed by a relatively strong polymeric/copolymeric film, such as relatively transparent or translucent polyethylene film. The interleaved sheets of paper function to impede corrosion of glass, prevent scratches and damp shocks, thereby safeguarding the glass sheets, which otherwise may be broken or cracked by relative movement/collision therebetween, as when such stacked and palletized sheets are transported to an end user.
Interleaving a sheet of paper between glass lites has in the past been done manually and is, therefore, time-consuming and costly from a production standpoint.
U.S. Pat. No. 4,807,743 acknowledges the function of such paper sheets to impede corrosion of glass, prevent scratches, damp shocks and prevent glass sheet/lite breakage. However, this patent also recognizes that moisture which is absorbed by such large paper sheets can create chemical reactions with the glass which produce paper stains on the glass surfaces. Wrinkle patterns from the paper sheets are said to be transferable to the lites thereby rendering the same less attractive. Glass quality is also said to deteriorate as a result of surface weathering of the glass sheets due to moisture absorption by the paper sheets, particularly under high humidity conditions under which water droplets may form and drip upon the lites. This patent suggests as one solution to these problems the same conventional utilization of craft paper as spacer material, but associated therewith are bodies of desiccant material housed within an overwrap of the stacked glass. The overwrap is a polyethylene film having low water vapor transmission characteristics. While this patent proposes solutions to several problems, its disclosure is silent with respect to the continued conventionality of utilizing large sheets of paper as spacers between adjacent pairs of lites.
Another approach to protecting sheets of material against damage during stacking or packaging is found in U.S. Pat. No. 3,385,462 which first acknowledges the interposition of loose materials, such as straw, wool fiber and sawdust, between sheets of glass when they are packed for transportation, or to interpose sheets of relatively soft material, such as paper or corrugated cardboard. However, the patent goes on to state that these methods do not prevent surface damage to the sheets which may in some cases make them useless, particularly if they are of a very high quality glass or have been specially surface treated. This patent proposes the utilization of a plurality of spacing members, such as pads of polyurethane having coatings of pressure-sensitive adhesive on the opposite faces which contact the glass sheets. An alternative approach is the utilization of spacing members each having a head portion formed as a suction member and a stem portion which is relatively flat. Such pads or spacer members are positioned between the glass sheets. These spacers are costly because of the intricate configuration thereof and the amount of material associated with each, not to mention the high productivity costs involved in manually locating a plurality of such spacers between adjacent glass sheets.
U.S. Pat. No. 2,992,747 avoids the utilization of individual spacers of any type, yet protects the surfaces of glass sheets that are stacked together for storage, shipment or other handling by spraying or applying parting material, with or without filler, upon surfaces of the sheets to maintain the same spaced when in stacked relationship. Such parting material coatings adhere to the glass sheet surfaces and provide suitable space between adjacent surfaces of the stacked glass sheets. Problems associated with such protection involve air quality standards during application, but more importantly remains the end use task of removing the coatings incident to the utilization of the glass sheets.
U.S. Pat. No. 2,476,145 suggests electrostatically charging glass sheets as they travel along a conveyor through the utilization of a silk cloth roll. Each glass sheet is thereby electrostatically charged. The electrostatically charged glass sheets are conveyed through an atmosphere filled with wood flour which causes the particles of flour to be attracted to the charged surfaces of the glass sheets in a relatively thin uniform layer. By negatively electrostatically charging the wood flour, the latter will be attracted and retained for a sufficient time to achieve stacking and wrapping of the glass sheets.
The invention is directed to a novel method of manufacturing a stack of lites (glass sheets or plates) in spaced relationship to each other to thereby prevent damage, particularly during shipment. The lites are successively fed along a first path of travel and thin spacers are fed along a second path of travel with the paths of travel converging toward an area of merger at which the thin spacers are adhered to the lites. The lites are thereafter stacked with the thin spacers sandwiched between adjacent pairs of the lites.
The thin spacers are carried by a ribbon formed of first and second relatively narrow strips of material. First surfaces of the two strips of material are in surface-to-surface abutting relationship, and a plurality of unending preferably circular cut lines are formed substantially through the first strip of material to set-off successive spacers which are carried by the second strip of material after removal of first strip waste material. Each spacer has associated therewith indicia means for activating a sensor to effect timed removal of the spacers from the second strip and the timed transfer thereof to an associated lite. The sensor activating means is preferably a dark line or bar of printed indicia associated with each spacer which is conventionally sensed to control ribbon feed in timed relationship with edge sensing of the conveyed lites. Preferably, at least two spacers are applied to each lite with one spacer being applied relative to leading edge sensing of the lite and the second spacer being applied responsive to trailing edge sensing of the lite. After each lite has applied thereto at least two such spacers, the lites are stacked upon a pallet, are appropriately wrapped in conventional film, and can be readily transported absent deterioration or damage because of the protection afforded by the spacers.
In further accordance with this invention, the relatively thin spacers are designed not only for spacing and thereby protecting the lites, but perhaps as importantly is the fact that the spacers can be readily removed incident to end use applications. For example, the lites can be glass shelves for refrigerators which are shipped from the lite manufacturer/fabricator in stacks to the refrigerator manufacturer. Each thin spacer must be readily removed by the manufacturer or the eventual end user, namely, the retail purchaser. To the latter end the spacers each include first and second surface areas which contact an associated lite. The first surface area of each spacer is in substantially adhering relationship to the lite, while the second surface area is in substantially nonadhering relationship to the lite. Therefore, the adhered first surface areas function to retain the spacers in position upon the lites during fabrication, stacking and shipment, while the second surface areas permit the spacers to be readily grasped and removed from the lites, either by the end use manufacturer or the end use retail user.
Preferably, each first surface area of each spacer possesses either adhesive characteristics or static cling (electrostatic) characteristics. In the first case, each spacer is preferably made of paper and includes on its first surface area a relatively weak bonding adhesive, while the second surface area excludes adhesive. Alternatively, both the first and second surface areas may be provided with a weak bonding adhesive, but the second surface areas are covered with a very thin covering, such as a thin piece of paper. In such case, the thin piece of paper or tab prevents the second surface areas from adhering to the lites and facilitates subsequent end use removal.
In lieu of the paper spacers, the spacers may also be made of material possessing static cling characteristics (electrostatically adherent to glass). Static cling vinyl or similar polymeric/copolymeric material is preferably utilized, and absent other provisions, each such static cling vinyl spacer readily adheres to an associated lite. However, the adherence is so relatively dramatic that difficulties could be encountered unless otherwise provided for, as, for example, difficulty of end-use removal, difficulty of glass separation, and the like. Accordingly, a first surface of each spacer includes a first surface area which possesses static cling or electrostatic adhering characteristics for adhering each spacer to an associated lite, but an adjacent second surface area is covered by a thin tab of nonadhering material, such as thin paper, which prevents such adherence. Thus, each spacer is electrostatically adhered to the lite at its first surface area, yet can be readily removed by grasping the second surface area/tab. Spacer transfer between stacked lites is prevented by coating each spacer opposite second surface with a U.V. coating or its equivalent which kills or suppresses static and prevents spacer transfer between adjacent stacked lites.
With the above and other objects in view that will hereinafter appear, the nature of the invention will be more clearly understood by reference to the following detailed description, the appended claims and the several views illustrated in the accompanying drawings.